DE102015113071B4 - Potential-shifting half-bridge, pole-reverser and reactive power inverters as well as Polwendeverfahren - Google Patents

Abstract

A half bridge (1) having a first input terminal (2); a second input terminal (3); an output terminal (4); a first bridge switch (S1) connected between the first input terminal (2) and the output terminal (4); a second bridge switch (S2) connected between the second input terminal (3) and the output terminal (4), a first additional bridge switch (S3) connected between the first input terminal (2) and the output terminal (4) and one between the second Input terminal (3) and second auxiliary bridge switch (S4) connected to the output terminal (4), characterized in that the first additional bridge switch (S3) and the second additional bridge switch (S4) are respectively connected in series with a reverse voltage compensator (32) parallel to the respective one Bridge switch (S1, S2) between the respective input terminal (2, 3) and the output terminal (4) are connected, wherein the Gegenspannunun gskompensator (32) is designed so that it is closed instead of the first bridge switch (S1) closed first additional bridge switch (S3) or instead of the second bridge switch (S2) closed second additional bridge switch (S4), the electrical potential of the respective input terminal (2, 3 ) shifts with respect to the output terminal (4) by a compensation voltage dropping above it and thus compensates for a reverse voltage between the output terminal (4) and the respective input terminal (2, 3) which is a current flow from the respective input terminal (2, 3) to the output terminal (4) is directed against.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a half bridge with the features of the preamble of independent claim 1, a Polwender with such a half bridge, an inverter with such a half bridge and in particular with such a Polwender and a Polwendeverfahren with the features of the preamble of independent claim 18th

STATE OF THE ART

From the DE 10 2014 102 000 B3 For example, there is known a method of operating a blind power inverter that includes a pole turning method. The powered using the known Polwendeverfahrens blind power inverter has a bidirectional DC / DC converter, a voltage intermediate circuit and a Polwender, the two poles of the voltage intermediate circuit by means of the Polwenders are alternately connectable to two terminals of an AC output to the polarity of the AC output relative to the Change voltage intermediate circuit. This change takes place at the zero crossing of an AC voltage applied to the AC output. In the case of a phase shift between alternating current and alternating voltage at the alternating current output, the direction of a current flowing through the voltage intermediate circuit is additionally reversed if the polarity of the alternating current output with respect to the voltage intermediate circuit is changed with the polarity reverser between the half waves of the alternating voltage. When the alternating current of the alternating voltage lags the alternating current output, the alternating current output is disconnected from the voltage intermediate circuit during reversal of the direction of the current flowing through the voltage intermediate circuit and a freewheeling path is provided between the two terminals of the alternating current output. For this purpose, the two terminals of the AC output are short-circuited, in particular via bridge switch of the Polwenders. In order to reverse the direction of the current flowing through the voltage intermediate circuit, the voltage intermediate circuit is charged with a current flowing through a storage choke device of the DC / DC converter and discharged in the opposite direction after the decay of this current. In the case of the alternating voltage at the alternating current output leading alternating current, these measures are not necessary when changing the polarity of the alternating current output with respect to the voltage intermediate circuit because a direct voltage applied to the voltage intermediate circuit acts as a driving force for this purpose.

That from the DE 10 2014 102 000 B3 Although known method avoids the high harmonic distortion, which is connected to other methods for operating a reactive power inverter with a DC / DC converter, a voltage source and a Polwender, but it requires a bidirectional DC / DC converter and a precise tuning of the DC link and the storage throttle device of the DC / DC converter to each other. Thus, it is also not possible to connect a plurality of DC / DC converters in parallel to the DC intermediate circuit in order to feed, for example, the electrical power of a plurality of photovoltaic generators operated with the respective DC / DC converter in their optimized operating point via a common pole inverter into an AC network.

From the CN 103208935 A For example, there is known a method of operating a reactive power inverter that incorporates a pole reversing method having the features of the preamble of independent claim 18. The powered using the known Polwendeverfahrens blind power inverter has a bidirectional DC / DC converter, a voltage intermediate circuit and a Polwender, the two poles of the voltage intermediate circuit by means of the Polwenders are alternately connectable to two terminals of an AC output to the polarity of the AC output relative to the Change voltage intermediate circuit. This change occurs at the zero crossing of an alternating current flowing through the AC output. The DC / DC converter comprises a step-down converter connected to a DC voltage source and a step-up converter effective in the opposite direction. The buck converter switch, the boost converter diode and a choke used by both steep are each divided into two components, so that there is a symmetrical arrangement. The boost converter is connected to the DC voltage source via the boost converter diode, which is divided into two diodes and has the opposite polarity to the buck converter. At the same sign of the alternating current and the AC voltage at the AC output of the buck converter of the DC / DC converter is active. However, if the AC voltage has its zero crossing before the zero crossing of the alternating current, the boost converter of the DC / DC converter is activated instead of the buck converter. Then, the intermediate circuit is connected to the DC voltage source via the boost converter, wherein the polarity with respect to the connection of the intermediate circuit with the DC voltage source is reversed via the buck converter.

A half-bridge with the features of the preamble of independent claim 1 results when two bridge switches are connected in parallel between the output terminal and each input terminal of a conventional half-bridge in order to increase the current carrying capacity of the half-bridge.

OBJECT OF THE INVENTION

The invention has for its object to provide a half-bridge, a Polwender, a blind power inverter and a Polwendeverfahren with which a reactive power without increasing the harmonic distortion and without any special requirements for circuits arranged in front and without coordination of the half-bridge and the Polwenders on preceding circuits is reached.

SOLUTION

The object of the invention is achieved by a half bridge with the features of independent claim 1, a pole turner according to the independent claim 11, an inverter according to the independent claims 12 or 13 and a Polwendeverfahren with the features of independent claim 18. The dependent claims relate to preferred embodiments of the invention half-bridge, the Polwenders invention, the inverter according to the invention and the Polwendeverfahrens invention.

DESCRIPTION OF THE INVENTION

In a half bridge according to the invention with a first input terminal, a second input terminal, an output terminal, a first bridge switch connected between the first input terminal and the output terminal, a second bridge switch connected between the second input terminal and the output terminal, a first connected between the first input terminal and the output terminal additional bridge switch and a second additional bridge switch connected between the second input terminal and the output terminal, the first additional bridge switch and the second additional bridge switch are each connected in series with a reverse voltage compensator between the respective input terminal and the output terminal. When the first additional bridge switch is closed instead of the first bridge switch or the second additional bridge switch is closed instead of the second bridge switch, the negative voltage compensator compensates for a reverse voltage between the output terminal and the respective input terminal, which counteracts a current flow from the respective input terminal to the output terminal. The negative voltage compensator shifts the electrical potential of the respective input terminal relative to the output terminal by a compensation voltage dropping above it. The counter voltage compensator thus makes it possible, in particular, to output reactive power via the half bridge according to the invention, without requiring any bi-directional or directly reactive power circuit or high-frequency triggering of the bridge switches of the half bridge.

In particular, the reverse voltage compensator may include a compensation voltage-chargeable first capacitor connected to the first additional bridge switch between the first input terminal and the output terminal and a compensation voltage-chargeable second capacitor connected to the second additional bridge switch between the second input terminal and the output terminal is switched on. The capacitors compensate with their compensation voltage counter to the current flow countervoltage, or in other words, they provide the compensation voltage for the potential shift of the respective input terminal relative to the output terminal.

In semiconductor switches with inherent anti-parallel diodes or body diodes typically used for the formation of half-bridges, each of the two capacitors of the back voltage compensator is to be connected in series with a discharge blocking diode between the respective input terminal and the output terminal which prevents its discharge and thus the drop in its compensation voltage. When bidirectionally blocking in the open state additional switches such discharge blocking diodes are not required.

Each of the two capacitors can be charged to the compensation voltage by closing the respective additional bridge switch. This also means that the capacitor continues to charge when the back voltage compensator is used. Accordingly, a discharge circuit is expediently provided for the first and the second capacitor of the negative voltage compensator, which regularly eliminates this additional charging of the capacitors. Although the discharge of the capacitors can basically also take place via a discharge resistor, it is preferred to discharge the capacitors while charging any usable intermediate circuit. This can be for example be on the input side or the output side of the half-bridge intermediate circuit or a DC link of a vehicle electrical system of the half-bridge.

The discharge circuit may have two separate discharge subcircuits, each associated with one of the two capacitors.

When the first capacitor and the second capacitor are arranged in front of the respective component, which prevents its discharge when the additional bridge switch is open, viewed from the output terminal, the discharge circuit can, viewed from the output terminal, have a first input terminal behind the first capacitor and a second input terminal behind the first capacitor having a second capacitor; So it comes with a total of two input terminals, between which the two capacitors are connected in series and over which the two capacitors can be discharged as a single. It is understood that the input terminals of the discharge circuit must be arranged in front of the respective component, which prevents discharge of the respective capacitor when the additional bridge switch is open. This component is the respective additional bridge switch itself, if it blocks bidirectionally, or the respective discharge blocking diode. If the respective additional bridge switch does not block bidirectionally, it can be arranged on either side of the respective capacitor and the respective input terminal of the discharge circuit.

The discharge circuit may have a simple flyback converter for discharging the capacitors concretely.

The discharge circuit may be designed such that it regularly sets a predetermined basic value of the compensation voltages when the additional bridge switches are open. This means that the discharge circuit regularly sets the default value of the compensation voltage, not that it necessarily does this every time the two additional bridge switches are opened. Rather, the setting can also be done at greater intervals. Although the predetermined base value of the compensation voltages is fixed for constant operating conditions of the half-bridge and thus in particular for constant maximum reverse voltages and, for example, at least as great as these occurring counter-voltages, it is clear that with varying counter-voltages the predetermined basic value of the compensation voltages tracks the variations of the counter-voltage can be and is usefully also tracked.

In principle, the negative voltage compensator may comprise, as an alternative to two capacitors, an ohmic resistance or a choke, in order to allow it to drop the opposite voltage and thus decouple the input side and the output side of the half-bridge. Neither the ohmic resistance, with which a resistance element is meant here, nor the inductance of the negative voltage compensator would be charged before use, so that an ohmic resistance or a choke between the output terminal and a branch to the additional bridge switches is sufficient. In the case of an ohmic resistance to drop the counter-voltage, however, considerable power loss would be incurred; and with a choke, care should be taken that it does not influence the flow of current beyond the desired level.

A switch driver for the half bridge according to the invention is preferably designed such that it in each case complementary to one another those of the bridge switches and those of the additional bridge switches, which are arranged between the output terminal and the same of the input terminals. This means that it closes at most one of these two bridge switches at any one time; there may also be times at which both bridge switches located between the output terminal and the same one of the input terminals are opened. As already indicated, the bridge switches of the half bridge according to the invention are not necessarily intended for higher frequency clocking. In any case, they can also be closed simultaneously for comparatively short part-time periods, for example, therefore, the respective bridge switch can be closed overlapping with the opening of the associated additional bridge switch and vice versa.

In a pole reverser according to the invention, in addition to the half-bridge according to the invention, a further half-bridge is arranged between the first input terminal and the second input terminal, which leads to a further output terminal. The further half-bridge of the Polwenders can likewise be a half-bridge according to the invention with further additional bridge switches and further counter-voltage compensator, but also a conventional half-bridge with only two further bridge switches.

Reactive power can be fed into an AC network with the pole turner according to the invention, without the need for a bidirectional or, in turn, reactive power circuit on the input side of the pole reverser. Accordingly, the invention Polwender as well as the invention half bridge be output side part of a reactive power inverter. In such an inverter according to the invention, an input-side DC / DC converter for forming a pulsating in sinusoidal half-waves direct current can be provided, which is output via the Polwender as alternating current. In this case, the at least one input-side DC / DC converter can be a single-quadrant controller, which therefore outputs its direct current via a DC intermediate circuit, so that the direct current and the voltage of the DC intermediate circuit always have the same sign. The inventive compensation of the back voltage or potential shift between the output terminals and the input terminals still allows electrical energy to be fed via the Polwender in an AC network in which a phase shift between AC and AC voltage occurs, so that AC and AC voltage have temporarily opposite signs. In the periods of these opposite signs, the AC voltage opposite the alternating current to the input of the Polwenders compensated or in other words, the potential of the input of the Polwenders relative to its output shifted so that from the point of view of the input of the DC always in the by the at the input applied DC voltage predetermined direction flows, even if AC and AC voltage at the output have different signs.

In the inverter according to the invention, several DC / DC converters with their respective outputs can be connected on the input side to a common DC voltage intermediate circuit. Via this common DC voltage intermediate circuit, the plurality of DC / DC converters together output the half-wave pulsating direct current to the polarity reverser, which is then assembled by the polarity reverser with half-wave alternating polarity to the desired alternating current. The additional bridge switch and the negative voltage compensator in the pole reverser according to the invention must therefore be provided only once for all connected DC / DC converters together. However, the input side DC / DC converters must be tuned to each other so that they work synchronously, d. H. output their pulsating direct current in parallel with the zero crossings of an alternating current starting and ending half-waves. However, this is a basic requirement for the supply of alternating current to an AC grid anyway.

At each of the input side DC / DC converter of the inverter according to the invention, a separate photovoltaic generator may be connected, whose operating point is set by the respective DC / DC converter. Thus, the respective DC / DC converter in addition to the current shaping and MPP tracking, d. H. a performance optimization of the respective photovoltaic generator can be used.

A switch drive of the inverter according to the invention is, as already indicated, preferably designed so that it changes the connection of the two output terminals of the Polwenders with the two input terminals at each zero crossing of the alternating current flowing between the output terminals and that they in periods in which an alternating voltage at the output terminal has a different sign than the alternating current, at least one of the additional switch instead of the corresponding switch of the half-bridge or the further half-bridge of the Polwenders closes. Thus, in the periods of different sign of AC and AC voltage between the output terminals, the potential shift is activated by means of the counter voltage compensator of the respective half-bridge.

In a Polwendeverfahren invention for alternately connecting two poles of a DC intermediate circuit with output terminals of an AC output to which an AC voltage is applied to output via the AC output an alternating current with a phase shift to the AC voltage, the connection of the output terminals of the AC output to the poles of the DC intermediate circuit Alternating zero crossing of the alternating current and the AC output is connected at the same sign of the AC and the AC voltage directly to the DC intermediate circuit, while it is connected at opposite signs of the AC and the AC voltage via a negative voltage compensator to the DC link. With the aid of this method, reactive power can be output at the AC output, although a DC current flows through the DC intermediate circuit and a DC voltage is applied to the DC intermediate circuit. H. DC and DC voltage here always have the same or at least no different signs.

The counter-voltage compensator can in particular be arranged and configured as described in connection with the half-bridge according to the invention. For the Polwendeverfahren invention but it is only important that the AC output selectively at opposite signs of the alternating current and the AC voltage over the negative voltage compensator is connected to the DC intermediate circuit. The counter-voltage compensator can be formed in any way in the connection between the AC output and the DC link, for example, by an only partially closed bridge switch or connected in series with a bridge switch or an output terminal, additional and opposite signs of the AC and AC voltage only partially opened flow valve. Such a partially closed bridge switch may be a semiconductor switch in linear operation. Such an only partially open flow valve may be a normally-conductive transistor which is driven to a desired voltage drop and thus forms a variable impedance.

For the reverse voltage compensation, a first capacitor of the back voltage compensator may be charged to a first compensation voltage between the one pole of the DC link and one of the output terminals of the AC output and a second capacitor of the back voltage compensator to a second compensation voltage between the other pole of the DC link and the one of the output terminals of the AC output , The charging of the two capacitors takes place by the current flowing from the DC voltage intermediate circuit to the AC output via the capacitor. This means at the same time that the charging of the capacitor is continued when the counter-voltage compensator is used. This means that the voltage applied across the respective capacitor basically increases until the voltage across both capacitors reaches the maximum voltage of the DC intermediate circuit. However, for the reverse voltage compensation, a compensation voltage across each of the capacitors is sufficient, which is equal to the maximum AC voltage of opposite sign to the AC current appearing at the AC output. An additional compensation voltage would cause unnecessary potential jumps of the DC intermediate circuit with respect to the AC output when the counter voltage compensator is activated. Therefore, it makes sense that the capacitors are regularly discharged back to a predetermined base value of the first and the second compensation voltage.

Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and of combinations of several features mentioned in the description are merely exemplary and can take effect alternatively or cumulatively, without the advantages having to be achieved by embodiments according to the invention. Without altering the subject matter of the appended claims, the following applies to the disclosure content of the original application documents and the patent: Further features can be found in the drawings - in particular the illustrated relative arrangements of several components and their operative connections. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims. Likewise, in the claims listed features for further embodiments of the invention can be omitted.

The features mentioned in the patent claims and the description are to be understood in terms of their number that exactly this number or a greater number than the said number is present, without requiring an explicit use of the adverb "at least". For example, when talking about an element, it should be understood that there is exactly one element, two elements or more elements. These features may be supplemented by other features or be the only characteristics that make up the product in question.

The reference numerals contained in the claims do not limit the scope of the objects protected by the claims. They are for the sole purpose of making the claims easier to understand.

list of figures

• 1 zeigt eine erfindungsgemäße Halbbrücke.
• 2 zeigt einen erfindungsgemäßen Polwender.
• 3 zeigt einen erfindungsgemäßen Wechselrichter.
• 4 zeigt den Verlauf eines Wechselstroms und einer Wechselspannung an einem Wechselstromausgang des Wechselrichters gemäß 3.
• 5 zeigt den Verlauf eines pulsierenden Gleichstroms über und den Verlauf einer Gleichspannung an einem Gleichspannungszwischenkreis des Wechselrichters gemäß 3.
• 6 illustriert die Ansteuerung von Brückenschaltern eines Polwenders des Wechselrichters gemäß 3; und
• 7 illustriert eine Ausführungsform einer Entladeschaltung der Halbbrücke gemäß 1, des Polwenders gemäß 2 oder des Wechselrichters gemäß 3.

In the following the invention will be further explained and described with reference to preferred embodiments shown in the figures.

• 1 shows a half bridge according to the invention.
• 2 shows a Polwender invention.
• 3 shows an inverter according to the invention.
• 4 shows the course of an alternating current and an alternating voltage at an alternating current output of the inverter according to 3 ,
• 5 shows the course of a pulsating direct current over and the course of a DC voltage at a DC voltage intermediate circuit of the inverter according to 3 ,
• 6 illustrates the control of bridge switches of a pole inverter of the inverter according to 3 ; and
• 7 illustrates an embodiment of a discharge circuit of the half-bridge according to FIG 1 , the Rev. according to 2 or the inverter according to 3 ,

DESCRIPTION OF THE FIGURES

In the 1 illustrated half-bridge 1 is between two input terminals 2 and 3 , between which a DC voltage U _DC is applied, arranged and connects the input terminals 2 and 3 alternatively with an output connection 4 , on the opposite to a reference point 5 with a reference potential an AC voltage U _AC is issued. The half bridge 1 points between the input terminal 2 and the output terminal 4 a first bridge switch S1 and between the input terminal 3 and the output terminal 4 a second bridge switch S2 on. Parallel to the bridge switch S1 is a first additional bridge switch S3 with a first capacitor C3 and a first discharge blocking diode D3 for the first capacitor C3 connected in series. Accordingly, it is parallel to the switch S2 a second additional bridge switch S4 with a second capacitor C4 and a second discharge-blocking diode D4 for the capacitor C4 connected in series. Here are the capacitors C3 and C4 first behind a branch 6 from the output terminal 4 to the two input terminals 2 and 3 arranged. Between the respective capacitor C3 respectively. C4 and the associated additional switch S3 or S4 is a discharge circuit 7 connected, with the two capacitors C3 and C4 can be unloaded if necessary. An uncontrolled discharge of the capacitors C3 and C4 is passed through the discharge blocking diodes D3 and D4 It prevents, in particular, a discharge over the opened switch S3 and S4 goes, which are typically formed as a semiconductor switch, the only unidirectionally lock in the open state.

When the capacitors C3 and C4 to a compensation voltage with the in 1 indicated polarities are charged what z. B. by temporarily closing the switch S3 and S4 can be effected, for example, leads to a connection of the output terminal 4 with the input connector 2 over the switch S3 instead of the switch S1 to that the potential of the input terminal 2 opposite the output terminal 4 around the over the capacitor C3 applied compensation voltage is shifted. This can be one over one via the output port 4 output AC temporarily negative sign of the AC voltage U _AC be compensated so that one from the input terminal 2 out of flowing current despite the negative instantaneous value of the AC voltage U _AC in through the between the input terminals 2 and 3 applied DC voltage U _DC predetermined direction flows. So can over the half bridge 1 Reactive power at the output terminal 4 can be output without being in between the input terminals 2 and 3 flowing direct current and the DC voltage applied in between U _DC ever give each other opposite signs. This is how the capacitors serve C3 and C4 as a counter voltage compensator 32 , the reverse voltages between the output terminal 4 and the respective input terminal 2 . 3 compensates for a current flow from the respective input terminal 2 . 3 to the output terminal 4 are directed against.

The Rev. Turner 8th according to 2 points next to the half bridge 1 according to 1 another half bridge 9 between the input terminals 2 and 3 on to another output terminal 10 alternatively with the input connections 2 and 3 connect to. The further half bridge 9 includes further bridge switches S5 and S6 , The bridge switches S1 to S6 the Polwenders are controlled by a switch control, not shown here, so that one of the two switches S1 and S3 together with the switch S6 or one of the two switches S2 and S4 together with the switch S5 is closed. By switching between these two forms of connection of the output terminals 4 and 10 with the input connections 2 and 3 becomes the polarity of the input terminals 2 and 3 opposite the output terminals 4 and 10 vice versa. As far as doing this instead of the switch S1 the desk S3 or instead of the switch S2 the desk S4 is closed, the already done by means of 1 explained potential shift of the DC voltage U _DC between the input terminals 2 and 3 opposite the AC voltage U _AC between the output terminals 4 and 10 ,

The in 3 illustrated inverter 11 includes the Rev. Turner 8th according to 2 with the half bridge 1 according to 1 , To the input terminals 2 and 3 are several DC / DC converters 12 to 14 connected in parallel, which are each sketched here as a buck converter. About the DC / DC converter 12 to 14 are separate photovoltaic generators 15 to 17 at one between the input terminals 2 and 3 formed DC intermediate circuit 18 connected. This DC voltage intermediate circuit 18 can as well as the DC / DC converter additional not shown Have capacitors. The individual DC / DC converters are simple single-quadrature controllers which synchronously produce a pulsed direct current via the DC voltage intermediate circuit 18 submit. The individual DC / DC converters 12 to 14 In this case, for example, they are driven so that they have an operating point of each connected photovoltaic generator 15 to 17 in the so-called MPP, the maximum power point, keep to that of the photovoltaic generators 15 to 17 maximize generated performance. The over the DC voltage intermediate circuit 18 flowing pulsed direct current is from the polarity reverser 8th to an alternating current between the output terminals 4 and 10 transformed by the polarity of the input terminals after each pulse, ie each half wave of the pulsed direct current 2 and 3 opposite the output terminals 4 and 10 turns. So is about the Rev. 8th an alternating current in on to the output terminals 4 and 10 connected AC mains fed.

4 shows the course of the alternating current I _AC relative to the course of the AC voltage U _AC between the output terminals 4 and 10 at a phase shift with the AC voltage U _AC leading alternating current I _AC , Due to the phase shift, time periods result 19 in which the AC voltage U _AC a different sign than the alternating current I _AC between the output terminals 4 and 10 Has. Reversing the polarity of the output terminals 4 and 10 opposite the input terminals 2 and 3 in the zero crossings of the alternating current I _AC , this in 5 is sketched, therefore, leads readily to the pulsating direct current I _DC over the DC intermediate circuit 18 , but basically also to voltage jumps 20 with a change of the sign at the DC voltage intermediate circuit 18 applied voltage Uz ie without countermeasures it would no longer be a DC voltage. This is compensated by, at least during the periods 19 the voltage Uz around the compensation voltage U _K attached to the capacitor C3 respectively. C4 is applied, is raised, so that the DC voltage U _DC without sign change results. The compensation voltage U _K can last even longer than over the time periods 19 remain activated so that the DC voltage U _DC then not to zero, but goes back to a value above zero. This is in 5 indicated by dotted lines.

6 illustrates the activation of the switches S1 to S6 of the Rev. 8th of the inverter 11 according to 3 to the DC voltage U _DC between the input terminals 2 and 3 according to 5 to reach. At a zero crossing of the alternating current I _AC at the time t ₀ is first for the period 19 next to the switch S6 the desk S3 closed. After the period 19 will at the time t ₁ from the switch S3 on the switch S1 , ie a direct connection without compensation voltage between the output terminal 4 and the input terminal 2 , switched. At the time t ₂ after a half-wave of the alternating current I _AC , ie at the next zero crossing, the switches S1 and S6 opened, and instead the switch S5 initially together with the switch S4 closed. After the period 19 is then from the switch S4 on the switch S2 switched.

7 shows a possible embodiment of the discharge circuit 7 , This is a flyback converter with a switch 31 that with a primary winding 21 a transformer 22 between input terminals 23 and 24 the discharge circuit 7 is connected in series. A secondary winding 25 of the transformer 22 is connected to a rectifier diode 26 between output terminals 27 and 28 the flyback converter connected in series, between which a smoothing capacitor 29 is arranged. The flyback converter outputs at the output terminals 27 and 28 a DC, which is galvanically isolated from the voltage between the input terminals 23 and 24 is and with the z. B. the DC intermediate circuit of a vehicle electrical system supply of the inverter 11 or an input-side DC intermediate circuit of one of the DC / DC converters 12 to 14 can be charged.

Instead of the two capacitors C3 and C4 can at the half bridge 1 according to 1 in a connection 30 the two half-bridges may also be provided with an ohmic resistance or a choke, around the output alternating voltage U _AC in the case of an opposite sign to the current flowing there I _AC from the DC voltage U _DC between the input terminals 2 and 3 with the help of one of the additional switches S3 respectively. S4 to decouple. Then the discharge blocking diodes D3 and D4 and the discharge circuit 7 not required. The control of the switches S1 to S4 at the half bridge 1 respectively. S1 to S6 on the other hand, the Polwender does not change. However, the desired potential shift occurs only with a current actually flowing through the ohmic resistance or the throttle current.

LIST OF REFERENCE NUMBERS

1

half bridge

2

input port

3

input port

4

output port

5

reference point

6

branch

7

discharge

8th

Rev.

9

half bridge

10

output port

11

inverter

12

DC / DC converter

13

DC / DC converter

14

DC / DC converter

15

photovoltaic generator

16

photovoltaic generator

17

photovoltaic generator

18

Dc link

19

Period

20

voltage jump

21

primary

22

transformer

23

input port

24

input port

25

secondary winding

26

Rectifier diode

27

output port

28

output port

29

capacitor

30

connection

31

switch

32

Gegenspannungskompensator

S1

first bridge switch

S2

second bridge switch

S3

first additional bridge switch

S4

second additional bridge switch

S5

first further bridge switch

S6

second additional bridge switch

C3

first capacitor

C4

second capacitor

D3

Entladesperrdiode

D4

Entladesperrdiode

U _DC

DC

U _AC

AC

Uz

uncompensated DC link voltage

U _K

compensation voltage

I _DC

pulsating direct current

I _AC

alternating current

t

Time

t ₀

time

t ₁

time

t ₂

time

Claims (20)

Half bridge (1) with - a first input terminal (2); a second input terminal (3); - an output terminal (4); a first bridge switch (S1) connected between the first input terminal (2) and the output terminal (4); - one between the second input terminal (3) and the output terminal (4) connected second bridge switch (S2); a first additional bridge switch (S3) connected between the first input terminal (2) and the output terminal (4) and a second additional bridge switch (S4) connected between the second input terminal (3) and the output terminal (4); characterized in that the first additional bridge switch (S3) and the second additional bridge switch (S4) each in series with a reverse voltage compensator (32) parallel to the respective bridge switch (S1, S2) between the respective input terminal (2, 3) and the output terminal (4) are connected, wherein the Gegenspannungskompensator (32) is adapted to be in instead of the first bridge switch (S1) closed first additional bridge switch (S3) or instead of the second bridge switch (S2) closed second additional bridge switch (S4) the electric Potential of the respective input terminal (2, 3) relative to the output terminal (4) shifts by a decreasing over him compensation voltage and thus a counter voltage between the output terminal (4) and the respective input terminal (2, 3) compensated, the current flow from the respective input terminal (2, 3) towards the output terminal (4) is directed. Half bridge (1) to Claim 1 characterized in that the back voltage compensator (32) is connected to a first compensation voltage (U _k ) chargeable first capacitor (C3) connected to the first additional bridge switch (S3) between the first input terminal (2) and the output terminal (4) and a second capacitor (C4) chargeable to a second compensation voltage (U _K ) connected to the second additional bridge switch (S4) between the second input terminal (3) and the output terminal (4). Half bridge (1) to Claim 2 characterized in that the first capacitor (C3) is connected in series with a first discharge blocking diode (D3) and the second capacitor (C4) is connected in series with a second discharge blocking diode (D4) between the respective input terminals (2, 3) and the output terminal (4 ) is switched. Half bridge (1) to Claim 2 or 3 , characterized in that a discharge circuit (7) for the first capacitor (C3) and the second capacitor (C4) is provided. Half bridge (1) to Claim 4 , characterized in that the discharge circuit (7) is designed such that it charges a DC link. Half bridge (1) to Claim 4 or 5 , as far as referring back to Claim 3 , characterized in that the first capacitor (C3) and the second capacitor (C4) are arranged in front of the respective discharge blocking diode (D3, D4) as seen from the output terminal (4) and that the discharge circuit (7) is arranged from the output terminal (4). from a first input terminal (23) behind the first capacitor (C3) and a second input terminal (24) behind the second capacitor (C4). Half bridge (1) to Claim 4 . 5 or 6 , characterized in that the discharge circuit (7) comprises a flyback converter. Half bridge (1) after one of Claims 4 to 7 , characterized in that the discharge circuit (7) is designed such that it regularly adjusts a predetermined basic value of the compensation voltages (U _K ) when the additional bridge switches (S3, S4) are open. Half bridge (1) to Claim 1 , characterized in that the counter voltage compensator (32) comprises an ohmic resistance or a choke. A half-bridge (1) according to any one of the preceding claims, characterized in that a switch driver is arranged to connect either of the output terminals (4) to one of the input terminals (2, 3) to those of the bridge switches (S1, S2) or those of Figs additional bridge switch (S3, S4), which are arranged between the output terminal (4) and the same of the input terminals (2, 3). Rev. Turner (8) with - A half-bridge (1) according to one of the preceding claims and - A further half-bridge (9), one between the first input terminal (2) and a further output terminal (10) connected first further bridge switch (S5) and between the second input terminal (3) and the further output terminal (10) connected second further Bridge switch (S6) has. Inverter (11) with at least one output half bridge (1) according to one of Claims 1 to 10 , Inverter (11) with - at least one input-side DC / DC converter (12 to 14) for shaping a pulsating in half-wave DC current (I _DC ) and - an output-side pole turner (8) Claim 11 for outputting an alternating current (I _AC ). Inverter (11) to Claim 13 , characterized in that the at least one DC / DC converter (12 to 14) is a single quadrant controller. Inverter (11) to Claim 13 or 14 , characterized in that the input side, a plurality of DC / DC converters (12 to 14) are connected with their respective outputs to a common DC voltage intermediate circuit (18) which is connected to the first and the second input terminal (2, 3). Inverter (11) to Claim 15 , characterized in that at each input side DC / DC converter (12 to 14), a separate photovoltaic generator (15 to 17) is connected, wherein the respective DC / DC converter (12 to 14) is formed so that it the operating point of the photovoltaic generator connected to it (15 to 17) pretends. Inverter (11) according to one of Claims 12 to 16 characterized in that a switch driver is arranged to connect the two output terminals (4, 10) to the two input terminals (2, 3) at each zero crossing of the alternating current (I _AC ) flowing between the output terminals (4, 10). and that in periods (19) in which an alternating voltage (U _AC ) between the output terminals (4, 10) has a different sign than the alternating current (I _AC ), at least one of the additional switches (S3, S4) instead of corresponding switch (S1, S2) of the half-bridge (1) or the further half-bridge (9) of the pole reverser (8) closes. Polwendeverfahren for alternately connecting two poles of a DC intermediate circuit (18) having output terminals (4, 10) of an AC output to which an AC voltage (U _AC ) is applied to output via the _AC output an alternating current (I _AC ) with a phase shift to the AC voltage (U _AC ), the compound of Output terminals (4, 10) of the AC output to the poles of the DC intermediate circuit (18) at the zero crossing of the alternating current (I _AC ) is changed, characterized in that the AC output at the same sign of the alternating current (I _AC ) and the AC voltage (U _AC ) directly is connected to the DC intermediate circuit, while it is connected at opposite signs of the alternating current (I _AC ) and the AC voltage (U _AC ) via a negative voltage compensator (32) with the DC intermediate circuit (18), the electrical potential of the respective input terminal (2, 3) with respect to the output terminal (4) by an over shifts it decreasing compensation voltage. Polwendeverfahren after Claim 18 , characterized in that a first capacitor (C3) of the negative voltage compensator (32) is charged to a first compensation voltage (U _K ) between the one pole of the DC intermediate circuit (18) and one of the output terminals (4) of the AC output, and a second capacitor ( C4) of the negative voltage compensator (32) is charged to a second compensation voltage (U _K ) between the other pole of the DC link (18) and the one of the output terminals (4) of the AC output. Polwendeverfahren after Claim 19 , characterized in that the capacitors (C3, C4), if they are not connected to the DC voltage intermediate circuit (18) are regularly discharged to a predetermined base value of the first and the second compensation voltage (U _K ).

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